The present invention relates to an information processing system, apparatus, method, and storage medium for providing information via a network.
The assignee of the present invention has been proposed several systems in which data of a sensed image is provided from a camera server to a client via a general purpose network, such as the Internet, and displayed, and several apparatuses used in those systems.
Among those proposals, there is one in which a pan angle, a tilt angle, and a zoom ratio of a camera, connected to a server on a network, are allowed to be controlled by a remote client and an image sensed under the above control is transferred to the client via the network.
Further, there is an application called push-media. This is a technique of updating information in a server and transferring the updated information to a client. In the push-media, transference of information is performed by xe2x80x9cpushingxe2x80x9d image data to a user without the user being aware, and the user is able to always have the latest information without a wait. As for a system of this type, there is Castanet, available from Marbimba Inc., using the hyper text transfer protocol (HTTP).
The World Wide Web (WWW) system, which is the most popular system, at present, is realized using the HTTP. The HTTP operates in the following manner.
1) A client transmits a request to a server.
2) The server returns a response to the client.
In other words, a WWW browser, which is a client, transmits a request to a server, and the server returns a response to the request.
If push-media is provided, image information in a server can automatically be provided to a client using the HTTP. When the push-media is used, it looks as if various information is automatically transferred to a client (browser). However, regardless of how the transference of information looks to a user, the information is not independently transferred from the server; actually, the browser periodically sends inquiry to the server and the information is returned from the server in response to the inquiry by the browser. More specifically, the browser periodically transmits inquiry to the server, and only when it is confirmed that information has been updated in the server, then the browser obtains the information from the server. Therefore, when the information is updated in the server, the client does not know of it without delay. A procedure for sending a request from the client to the server is necessary, thus, the time for the procedure cannot be omitted.
Further, it is possible to notifying a client of an occurred change in state on the side of a server without delay by performing a process of monitoring a change in state in the server and a process of receiving information on the change in the state by the client, and communicating between the server and the client using Transmission Control Protocol and Internet Protocol (TCP/IP). In this method, a protocol other than HTTP may be used, however, when a firewall exists, the method using TCP/IP does not work.
By comparison, HTTP is widely used, and it is possible to get over the firewall in most sites using HTTP. Therefore, it is desirable that a change in the state of the server be notified, from the server to the client, using HTTP.
Accordingly, a structure to immediately notify a change in state of the server to a client using HTTP is demanded.
The present invention has been made in consideration of the above situation, and has as its object to provide an information processing system, apparatus, method, and recording medium capable of enabling to a reduction in traffic of a network by omitting the transmission of information when the information has not changed.
It is another object of the present invention to provide an information processing system, apparatus, method, and recording medium capable of overcoming the aforesaid problems by getting over the firewall.
According to the present invention, the foregoing object is attained by providing an information processing system including a server and a client connected to a network, wherein the server comprises: monitoring means for monitoring an occurrence of an event in information to be provided; and informing means for informing the client of information corresponding to the event on the basis of the monitoring by the monitoring means, and the client comprises: reception means for receiving notification from the informing means and performing processing on the basis of the contents of the notification.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings in which like reference characters designate the same or similar parts throughout the figures thereof.